Conventionally, in a hybrid drive force transmission device in which a dry clutch for selectively connecting and disconnecting driving force transmission is arranged in a clutch chamber that is partitioned by a partitioning seal, the partitioning seal structure with a resilient or elastic seal member and a transfer plate is known. See, for example, Japanese Laid-Open Patent Application No. 2010-151313.
The elastic seal member is positioned and fixed to a side wall of the clutch drum and is deformed to follow the stroke motion of the distal end portion of a piston arm. A transfer plate is provided integrally with the elastic sealing member, and at the engagement of the dry clutch, the transfer plate is brought into contact with a clutch plate to transmit clutch engagement force.
However, the conventional hybrid drive force transmission device of the prior art is configured to allow the transfer plate to make a surface contact with a front end surface of the front end of piston arm with the transfer plate and give the biasing force of a return spring to the piston arm only. Therefore, in the transition period of clutch release in which the dry clutch shifts from the engagement state to the release or open state, when the transfer plate is being in close contact with the clutch plate, the piston arm may be urged to retreat for a backward stroke prior to the transfer plate by the urging force of the return spring. In this instance, until the transfer plate has left the clutch plate, the problem of delay in clutch release response was encountered.
Further, in the open state of the dry clutch, the biasing force by the return spring is applied only to the piston arm, and the transfer plate is only elastically supported by the elastic seal member. Therefore, there is a problem that, when there is vibration input and the like to the transfer plate, the transfer plates vibrates along the input direction to contact the clutch plate thereby reducing the gap between clutch plates with causing the occurrence of drag between the clutch plates.